A liquid crystal display device is widely used as a display for portable electronic devices including portable telephones, television sets, and personal computers. Generally, the liquid crystal display device exhibits excellent display characteristics when a display screen is viewed from the front. Meanwhile, when a display screen is viewed from an oblique direction, a contrast is degraded and visibility is likely to be deteriorated. Otherwise, there may be an occurrence of grayscale inversion in which brightness is inverted in displaying grayscale. Therefore, various techniques to widen a viewing angle range so as to be able to observe the screen with favorable visibility have been proposed.
For example, PTL 1 discloses a liquid crystal display device including a liquid crystal cell and an optical compensation polarization plate. The optical compensation polarization plate is arranged on at least one side of a light incident side and a light emission side in the liquid crystal cell. The optical compensation polarization plate has a polarization plate, a birefringence layer, and an anisotropic scattering film.
In addition, PTL 2 discloses a liquid crystal display device including a liquid crystal display panel and a light diffusion sheet. The light diffusion sheet is arranged on a light emission side of the liquid crystal display panel. The light diffusion sheet has a low refractive index region and a high refractive index region. The cross-sectional shape of the low refractive index region is approximated to an isosceles triangle. The high refractive index region is arranged around the low refractive index region.